From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linutronix.de (193.142.43.55:993) by crypto-ml.lab.linutronix.de with IMAP4-SSL for ; 16 Oct 2019 07:14:37 -0000 Received: from mx1.redhat.com ([209.132.183.28]) by Galois.linutronix.de with esmtps (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iKdW0-0006sv-9F for speck@linutronix.de; Wed, 16 Oct 2019 09:14:36 +0200 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id EC42C302C085 for ; Wed, 16 Oct 2019 07:14:28 +0000 (UTC) Received: from treble (ovpn-120-161.rdu2.redhat.com [10.10.120.161]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6DC4A5C1B5 for ; Wed, 16 Oct 2019 07:14:28 +0000 (UTC) Date: Wed, 16 Oct 2019 02:14:25 -0500 From: Josh Poimboeuf Subject: [MODERATED] Re: [PATCH v5 08/11] TAAv5 8 Message-ID: <20191016071425.hagogacjohvbqjsz@treble> References: <20191015152649.yim4krwuttrh6xgi@treble> <20191015200024.hxs4brxi7gbvmcdy@treble> <20191015205631.GF30412@guptapadev.amr> <20191015231252.kggxh6ffrciz2dfy@treble> MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: speck@linutronix.de List-ID: On Wed, Oct 16, 2019 at 06:52:15AM +0200, speck for Jiri Kosina wrote: > yOn Tue, 15 Oct 2019, speck for Josh Poimboeuf wrote: > > > So if I understand correctly, you're postulating that distros want: > > > > a) TAA_BUG && MDS_NO=0 => TSX on > > b) TAA_BUG && MDS_NO=1 => TSX off > > c) !TAA_BUG => TSX on > > > > How are you reaching that conclusion? It seems horribly confusing for > > TSX users, but again maybe I'm missing something. > > > > It seems to me that "heavy users of TSX" would want tsx=on, no matter > > what. And so we would need to leave that as the default in order to not > > break those users. > > But then we're not defaulting to safe behavior, which is confusing too, > because we almost (SMT being the exception) always did in the past for all > the other previous issues. Why wouldn't it be safe behavior? For both TAA_BUG cases, we can mitigate TSX with verw buffer clearing. -- Josh